Heating & AC System: 33

33-A/C MODE SWITCH STUCK







Theory of Operation

The switch input changes when the switch is pushed down. A stored DTC 33 indicates that the A/C mode switch was stuck in a pushed position for more than 10 minutes, but has since returned to its normal state. An active DTC 33 indicates that the A/C mode switch is stuck in a pushed position. An active DTC 33 will prevent the control from entering diagnostic mode and performing certain diagnostic functions. It will also prevent proper A/C mode switch and status indicator function.

- When Monitored:
With the ignition on.

- Set Condition:
If the A/C mode switch stays in a pushed position for more than 10 minutes.





1. INSPECT THE A/C HEATER CONTROL FOR DAMAGE
1. Turn the ignition off.
2. Inspect the A/C Heater Control for damage.

Is the A/C Heater Control damaged?

Yes

- Replace the A/C Heater Control.
- Perform the BODY VERIFICATION TEST Body Verification Test.

No

- Go To 2

2. INSPECT FOR OBJECT OR SUBSTANCE CAUSING THE A/C MODE SWITCH TO STAY OR STICK IN A PUSHED POSITION
1. Inspect the A/C Heater Control for anything that would cause the A/C mode switch to stay or stick in a pushed position.

Is anything present that would cause the A/C mode switch to stay or stick in a pushed position?

Yes

- Repair as necessary.
- Perform the BODY VERIFICATION TEST Body Verification Test.

No

- Go To 3

3. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT VOLTAGE




1. Disconnect the A/C Heater Control C3 harness connector.
2. Turn the ignition on.
3. Measure the voltage of the (C41) Blower Switch Position Signal circuit.

What is the voltage?

Below 4.8 Volts

- Go To 4

Above 5.2 Volts

- Go To 7

4.8 Volts To 5.2 Volts

- Go To 8

4. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO THE (C121) SENSOR GROUND CIRCUIT




1. Turn the ignition off.
2. Disconnect the A/C Heater Control C2 harness connector.
3. Measure the resistance between the (C41) Blower Switch Position Signal circuit and the (C121) Sensor Ground circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10K ohms?

Yes

- Repair the (C41) Blower Switch Position Signal circuit for a short to the (C121) Sensor Ground circuit.
- Perform the BODY VERIFICATION TEST Body Verification Test.

No

- Go To 5

5. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance of the (C41) Blower Switch Position Signal circuit between ground and the A/C Heater Control C3 harness connector.

Is the resistance below 10K ohms?

Yes

- Repair the (C41) Blower Switch Position Signal circuit for a short to ground.
- Perform the BODY VERIFICATION TEST Body Verification Test.

No

- Go To 6

6. CHECK (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR AN OPEN




1. Measure the resistance of the (C41) Blower Switch Position Signal circuit between the A/C Heater Control C2 harness connector and the A/C Heater Control C3 harness connector.

Is the resistance below 5.0 ohms?

Yes

- Replace the A/C Heater Control.
- Perform the BODY VERIFICATION TEST Body Verification Test.

No

- Repair the (C41) Blower Switch Position Signal circuit for an open.
- Perform the BODY VERIFICATION TEST Body Verification Test.

7. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE




1. Turn the ignition off.
2. Disconnect the A/C Heater Control C2 harness connector.
3. Turn the ignition on.
4. Measure the voltage of the (C41) Blower Switch Position Signal circuit.

Is the voltage above 0.2 volts?

Yes

- Repair the (C41) Blower Switch Position Signal circuit for a short to voltage.
- Perform the BODY VERIFICATION TEST Body Verification Test.

No

- Replace the A/C Heater Control.
- Perform the BODY VERIFICATION TEST Body Verification Test.

8. CHECK FOR NORMAL A/C MODE SWITCH AND STATUS INDICATOR FUNCTION
1. Turn the ignition off.
2. Reconnect the A/C Heater Control C3 harness connector.
3. Turn the ignition on.
4. Turn the Blower control on.
5. Press the A/C mode switch on and off several times while observing the A/C status indicator.

Does the A/C status indicator turn on and off with respect to the switch position?

Yes

- Go To 9

No

- Replace the A/C Heater Control.
- Perform the BODY VERIFICATION TEST Body Verification Test.

9. CHECK A/C HEATER CONTROL OPERATION BY ATTEMPTING TO ENTER DIAGNOSTIC MODE
1. If illuminated, turn off the A/C status indicator and the EBL status indicator.
2. Actuate the display DTC function by performing the following:
- Turn the blower control on.
- Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.

3. When entry mode is recognized, the A/C status indicator and the EBL status indicator will illuminate for 5 seconds and then display DTCs, if present. The A/C status indicator displays active DTCs when the EBL status indicator is not illuminated and stored DTCs when the EBL status indicator is illuminated. However, if no DTCs are present, both status indicators will turn off and the system will exit diagnostic mode.

Did the A/C Heater Control enter diagnostic mode?

Yes

- Perform the BODY VERIFICATION TEST Body Verification Test.

No

- Replace the A/C Heater Control.
- Perform the BODY VERIFICATION TEST Body Verification Test.